A conventional annular combustion chamber is illustrated in FIG. 1. It is an axial half-section relative to the axis of the engine of such a chamber, the other half being deduced by symmetry relative to this axis. The combustion chamber 110 is housed in a plenum chamber 130 which is an annular space defined between an outer casing 132 and an inner casing 134, into which the compressed air is injected originating from an upstream compressor, not shown, via an annular distribution duct 136. This conventional combustion chamber 110 comprises an outer wall 112 and an inner wall 114 that are coaxial and substantially conical in order to make the connection between the compressor stream and the turbine stream. The outer wall 112 and internal wall 114 are connected together at the upstream end by a wall forming the chamber bottom 116.
The chamber bottom is an annular frustoconical part which extends between two substantially transverse planes while widening out from downstream to upstream. The chamber bottom is connected to each of the two walls 112 and 114 by annular flanges 116e and 116i. 
The chamber bottom is pierced with orifices 118 through which the systems 120 for injecting fuel premixed with the combustion air pass. These orifices are distributed angularly about the engine axis. Sources of combustion are produced downstream of the injection systems. The plane of the orifices is perpendicular to the axis of the combustion sources. In the example shown, the combustion sources with their axis 200 are divergent, forming an angle a relative to the axis of the engine.
To protect the chamber bottom from heat radiation, heat protection screens indicated as baffles 122 are provided. These baffles are substantially flat plates made of refractory material with an opening corresponding to that of the orifices of the injection systems. The baffles are centered on the latter and attached by brazing to the chamber bottom. They are cooled by jets of cooling air entering the chamber through cooling drill holes 124 in the chamber-bottom wall. These jets of air flowing from upstream to downstream are guided by chamber fairings 126, pass through the chamber bottom 116 and by impact cool the upstream face of the baffles 122.
Because of the conicity of the chamber-bottom wall, flat bearing surfaces are made around the orifices of the injection systems to which the baffle shoulders are applied. Since the chamber-bottom wall is a metal sheet, these bearing surfaces are made by local swaging. Dimpling ensures the connection between the swaged surface and the conical surface of the metal sheet.
Technological progress is leading to the production of larger-diameter injection systems. Furthermore efforts are being made to place combustion sources distributed about the axis of the chamber as close as possible to one another in order to obtain optimal combustion.
This then poses the problem of producing bearing surfaces by swaging in the narrowest zone between two adjacent orifices. The closeness of the orifices does not allow the production of these bearing surfaces by swaging.